The main reason for the drying speed of water-based paints is the resin!

Quick-drying is the most frequently heard customer request for water-based coatings
.
Due to the uniqueness of its molecular structure, that is, the strong hydrogen bonding between molecules, its characteristics are clearly different from most organic solvents
.
In the field of water-based coatings, this feature is concentrated in that, due to the high evaporation heat of water, the evaporation rate of water is ten times or even dozens of times slower than that of common coating solvents .
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Moreover, because the content of water vapor in the air is significant and changes greatly with the seasons, the evaporation rate of water changes accordingly
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In the most severe case, if the relative humidity of the air reaches 100%, the evaporation of water will stop, and the non-aqueous solvent will not be affected by this factor
.

Although water-based coatings face the above-mentioned technical challenges, they will inevitably become an important member of the coatings field due to their environmental protection characteristics

1.

Like all coatings, the performance of water-based coatings is largely determined by the resin used in the formulation
.
Most water-based film-forming resins are emulsion systems, and the film-forming mechanism of this system is different from that of solvent-based coatings
.
Solvent-based resin and solvent form a single-phase system.
As the solvent evaporates, the viscosity of the system increases until it becomes a solid.
In terms of the mechanical properties of the system, it is a continuous process
.
The water-based emulsion is a two-phase system.
With the evaporation of water, the viscosity of the system does not change much at the beginning, but when the volume of the emulsion particles in the total system volume reaches a critical value, the system suddenly changes from a commercial state to a solid state.
A discontinuous process, this critical point is the beginning of the surface drying of water-based paints, so the surface-drying time of water-based paints is shorter than that of some solvent-based paints
.
From the surface drying to the performance of the paint film, it depends on the evaporation rate of the residual water in the system, the interpenetration of the macromolecules in the emulsion particles, and the volatilization rate of other small organic molecules in the system
.
In order to optimize the system, when making water-based paint formulations, resins should be selected from the following aspects:

a.

b.

c.

d.

e.

2.

 Water-based resin film formation and curing generally have several levels of mechanism

3.

In theory, any resin solvent is a film-forming aid
.
In practice, considering factors such as safety, cost, speed, etc.
, there are only a dozen common film-forming aids, mainly some high-boiling alcohols, ethers and esters
.
These film-forming additives will have their own preferences for different water-based paint engineers
.
Generally, an experienced engineer usually uses only two or three kinds of film-forming additives
.
The main considerations are the distribution of reagents between water and resin and the distribution inside resin particles
.
Especially when the water-based resin is a multi-phase resin, the selection and matching of the film-forming aids becomes particularly important
.

4.
Construction environment:

 At the beginning of this article we discussed the issue of water
.
It is precisely because of the characteristics of water that the construction environment of water-based coatings is higher than that of oil-based paints.
The main purpose is to control the temperature and humidity during construction as much as possible
.
The construction of general formula should try to avoid high humidity environment
.
If construction must be carried out under high humidity, the formula should be adjusted, or a resin with fast film-forming properties should be selected or the site should be isolated
.